Boosting efficiency and stability of 2D alternating cation perovskite solar cells via rational surface-modification: Marked passivation efficacy of anion

Two-dimensional(2D) alternating cation(ACI) perovskite surface defects,especially dominant iodine vacancies(V_Ⅰ) and undercoordinated Pb^(2+),limit the performance of perovskite solar cells(PVSCs).To address the issue,1-butyl-3-methylimidazolium trifluoro-methane-sulfonate(BMIMOTF) and its iodide counterpart(BMIMI) are utilized to modify the perovskite surface respectively.We find that BMIMI can change the perovskite surface,whereas BMIMOTF shows a nondestructive and more effective defect passivation,giving significantly reduced defect density and suppressed charge-carrier nonradiative recombination.This mainly attributes to the marked passivation efficacy of OTF-anion on V_Ⅰ and undercoordinated Pb^(2+),rather than BMIMI^(+) cation.Benefiting from the rational surface-modification of BMMIMOTF,the films exhibit an optimized energy level alignment,enhanced hydrophobicity and suppressed ion migration.Consequently,the BMIMOTF-modified devices achieve an impressive efficiency of 21.38% with a record open-circuit voltage of 1.195 V,which is among the best efficiencies reported for 2D PVSCs,and display greatly enhanced humidity and thermal stability.

Daqing Oilfield Liquid Phase Underbalanced Drilling Improving Drilling Speed Evaluation Method

Factors affecting the drilling speed are very complex, such as formation factor (layers lithology, depth, porosity and reservoir pressure), fluid density, drilling parameters (bit pressure and speed), drill types, etc. Although liquid phase underbalanced drilling technology is to increase the penetration rate and shorten the drilling cycle, there is no evaluation model currently, so we cannot evaluate which factors can have a greater impact on speed. Based on the establishment of equivalent density and improvement of ROP (Rate of Penetration) calculation model, this paper is about the application of underbalanced drilling technology to improve drilling speed multiple sizes.

Vapor Phase Polymerization Deposition Conducting Polymer Nanocomposites on Porous Dielectric Surface as High Performance Electrode Materials

We report chemical vapor phase polymerization(VPP) deposition of poly(3,4-ethylenedioxythiophene)(PEDOT) and PEDOT/graphene on porous dielectric tantalum pentoxide(Ta_2O_5) surface as cathode films for solid tantalum electrolyte capacitors. The modified oxidant/oxidant-graphene films were first deposited on Ta_2O_5 by dip-coating, and VPP process was subsequently utilized to transfer oxidant/oxidant-graphene into PEDOT/PEDOT-graphene films. The SEM images showed PEDOT/PEDOT-graphene films was successfully constructed on porous Ta_2O_5 surface through VPP deposition, and a solid tantalum electrolyte capacitor with conducting polymer-graphene nano-composites as cathode films was constructed. The high conductivity nature of PEDOT-graphene leads to resistance decrease of cathode films and lower contact resistance between PEDOT/graphene and carbon paste. This nano-composite cathode films based capacitor showed ultralow equivalent series resistance(ESR) ca. 12 m? and exhibited excellent capacitance-frequency performance, which can keep 82% of initial capacitance at 500 KHz. The investigation on leakage current revealed that the device encapsulation process has no influence on capacitor leakage current, indicating the excellent mechanical strength of PEDOT/PEDOT-gaphene films. This high conductivity and mechanical strength of graphene-based polymer films shows promising future for electrode materials such as capacitors, organic solar cells and electrochemical energy storage devices.

Ordered SrTiO_3 Nanoripples Induced by Focused Ion Beam

Ordered nanoripples on the niobium-doped SrTiO_3 surfaces were fabricated through focused ion beam bombardment. The surface morphology of the SrTiO_3 nanoripples was characterized using in situ focused ion beam/scanning electron microscopy. The well-aligned SrTiO_3 nanostructures were obtained under optimized ion irradiation conditions. The characteristic wavelength was measured as about 210 nm for different ion beam currents. The relationship between the ion irradiation time and current and SrTiO_3 surface morphology was analyzed. The presented method will be an effective supplement for fabrication of SrTiO_3 nanostructures that can be used for ferroelectric and electronic applications.

Flexible optoelectronic devices based on metal halide perovskites

The unique physical and chemical properties of metal halide perovskites predestine the devices to achieve high performance in optoelectronic field.Among the numerous high qualities of perovskites,their different low-temperature synthesis methods and preparation processes make them impressive and popular materials for flexible optoelectronic devices.Mainstream perovskite devices,for instance,solar cells,photodetectors and light-emitting diodes,have been fabricated on flexible substrates and show outstanding flexibility as well as high performance.For soft wearable electronic systems,mechanical flexibility is the premier condition.Compared to common devices based on rigid substrates,flexible perovskite devices are more practical and see widespread applications in energy,detection,display,and other fields.This review summarizes the recent progress of flexible perovskite solar cells,photodetectors and light-emitting diodes.The design and fabrication of different high-performance flexible perovskite devices are introduced.Various low-dimensional perovskite materials and configurations for flexible perovskite devices are presented.In addition,the limitations and challenges for further application are also briefly discussed.

A survey on numerical simulations of drag and heat reduction mechanism in supersonic/hypersonic flows

Along with the survey on experimental investigations drawing attention to the drag and heat reduction mechanism, the authors simultaneously focus on the recent advances of numerical simulations on the schemes applied to supersonic/hypersonic vehicles. The CFD study has evolved as an irreplaceable method in scheme evaluation and aircraft optimization. Similar to our previous experimental survey, the advances in drag and heat reduction schemes are reviewed by similar kinds of mechanism in this article, namely the forward-facing cavity, the opposing jet, the aerospike, the energy deposition and their combinational configurations. This review article puts an emphatic eye on the flow conditions, numerical methods, novel schemes and analytical conclusions given in the simulations. Further, the multi-objective design optimization concept has also been illustrated due to the observable advantages of using CFD over experimental method, especially those performances conducted in drag reduction and thermal protection practice, and this would possess reference value in the design of aircraft system.

通过弱配位溶剂退火揭示钙钛矿薄膜生长机制（英文）

本研究在两步法沉积CH_3NH_3PbI_3和一步法沉积CsPbI_3薄膜过程中使用弱配位溶剂异丙醇(IPA)对钙钛矿及钙钛矿前驱体进行溶剂退火处理,从而揭示了钙钛矿薄膜的成核机理.同时研究了退火温度对两步法中PbI_2前驱体进行溶剂退火处理时的作用.发现IPA溶剂退火工艺严重影响了PbI_2和CH_3NH_3PbI_3薄膜的晶粒尺寸、致密度、粗糙度和薄膜形貌.相同的弱配位溶剂退火工艺也被应用于制备全无机CsPbI_3钙钛矿.通过溶剂退火可以得到具有均匀晶粒尺寸、连续致密的全无机CsPbI_3薄膜.我们认为弱配位溶剂退火工艺可以通过有效地调控钙钛矿中间相中的残留溶剂量来影响钙钛矿成膜中的再结晶过程.通过IPA溶剂退火工艺,CH_3NH_3PbI_3钙钛矿太阳能电池光电转换效率达到17.4%,而CsPbI_3的光电转换效率达到了2.5%.

Interface engineering of high efficiency perovskite solar cells based on ZnO nanorods using atomic layer deposition

Despite the considerably improved efficiency of inorganic-organic metal hybrid perovskite solar cells （PSCs）, electron transport is still a challenging issue. In this paper, we report the use of ZnO nanorods prepared by hydrothermal self- assembly as the electron transport layer in perovskite solar cells. The efficiency of the perovskite solar cells is significantly enhanced by passivating the interfacial defects via atomic layer deposition of Al2O3 monolayers on the ZnO nanorods. By employing the Al2O3 monolayers, the average power conversion efficiency of methylammonium lead iodide PSCs was increased from 10.33% to 15.06%, and the highest efficiency obtained was 16.08%. We suggest that the passivation of defects using the atomic layer deposition of monolayers might provide a new pathway for the improvement of all types of PSCs..